Google has kicked off a project to create an authoritative store of information about any and every topic.

The search giant has already started inviting people to write about the subject on which they are known to be an expert.

Google said it would not act as editor for the project but will provide the tools and infrastructure for the pages.

Many experts see the initiative as an attack on the widely used Wikipedia communal encyclopaedia.

'Knol'

Writing about the project on the official Google blog, Udi Manber, one of the heads of engineering at the search firm, said it was all about sharing useful knowledge.

By indexing the web, Google strives to make information more easily accessible. However, wrote Mr Manber, not all the information on the web was "well organised to make it easily discoverable".

By getting respected authors to write about their specialism Google hopes to start putting some of that information in better order.

The system will centre around authored articles created with a tool Google has dubbed "knol" - the word denotes a unit of knowledge - that will make webpages with a distinctive livery to identify them as authoritative.

Mr Manber wrote: "A knol on a particular topic is meant to be the first thing someone who searches for this topic for the first time will want to read."

The knol pages will get search rankings to reflect their usefulness. Knols will also come with tools that readers can use to rate the information, add comments, suggest edits or additional content.

Revenue from any adverts on a knol page will be shared with its author.

Industry commentator Nicholas Carr said the knol project was a "head-on competitor" with Wikipedia. He said it was an attempt by Google to knock ad-free Wikipedia entries on similar subjects down the rankings.